1. Field of the Invention
The present invention relates to a metal belt comprising a metal ring assembly including a plurality of layered endless metal rings and a large number of metal elements supported on the metal ring assembly. The metal belt is wound around pulleys and transmits a driving force.
2. Description of the Related Art
The published Japanese translation of PCT Application No. 2003-532840 discloses an arrangement in which, among a plurality of metal rings forming a metal ring assembly of a belt type continuously variable transmission, the nominal value of play between two adjacent metal rings is made negative on the innermost belt side, positive on the outermost belt side, and zero in a middle section therebetween, thus making tension acting on each metal ring constant to reduce variation in the life thereof.
However, the above-mentioned conventional arrangement does not take into consideration the problem that the innermost metal ring comes into contact with a saddle face of a metal element and receives a load higher than that acting on the other metal rings, and the further problem that when the amount of lubricating oil is small, the lubricating effect is degraded for metal rings outside a middle ring, and thus the side face of a metal ring receiving a high frictional force comes into dynamic contact with a metal ring contact face of a neck portion of the metal element and is worn, thus degrading the durability.